The integrated application of nZVI particles and a microbial consortium was very effective in improving plant growth, mitigating Cd-accumulation in plants, confirming Cd-immobilization, and removing PHCs from soil, highlighting the potential of nano-enhanced bioremediation as a sustainable solution for the treatment and management of soil co-contaminated with inorganic and organic pollutants.
Abstract
Simultaneously removing petroleum hydrocarbons (PHCs) and heavy metals from soil is a challenging task. This study aimed to evaluate the efficacy of green-synthesized nano zero-valent iron (nZVI) particles and a microbial consortium in combination with sunflower (
Helianthus annuus
L.) plants for nano-enhanced bioremediation of soil co-contaminated with PHCs and cadmium (Cd). A pot trial was conducted by growing sunflower plants on soil co-contaminated with 6000 mg kg
-1
and 30 mg kg
-1
of PHCs and Cd, respectively, and nZVI particles and a microbial consortium were added to the soil for plant growth enhancement and pollutants removal.
The results revealed that the co-contaminated soil caused significant phytotoxicity to sunflower plants. However, the co-application of a microbial consortium and nZVI particles considerably alleviated the phytotoxic impacts of Cd and PHCs on sunflower plants, demonstrating up to 72.7% and 83.5% improvements in plant physiology and growth in contaminated soil, respectively compared to the respective unamended control. Furthermore, the combined application of a microbial consortium and nZVI particles caused 59.4% and 58.6% reduction in bioavailable Cd, and 82.7% and 74.7% decrease in PHCs in planted and unplanted treatments, respectively, with respect to their initially applied concentrations.
The findings from this study indicate that the integrated application of nZVI particles and a microbial consortium was very effective in improving plant growth, mitigating Cd-accumulation in plants, confirming Cd-immobilization, and removing PHCs from soil, highlighting the potential of nano-enhanced bioremediation as a sustainable solution for the treatment and management of soil co-contaminated with inorganic and organic pollutants.
Conventional phytoremediation of heavy metal-contaminated industrial soils often fails to achieve desired outcomes due to limited metal accumulation capacity and low plant biomass. To overcome these limitations, we developed a synergistic micro-nano bubbles (MNBs)-ryegrass (Lolium perenne L.) remediation system. MNBs supply reactive oxygen species to mobilize heavy metals, thereby optimizing the rhizosphere microenvironment. The results demonstrated that MNBs treatment significantly stimulated both aboveground growth and biomass accumulation in ryegrass. Under high-polluted condition, the shoot length and dry weight increased by 41% and 88%, respectively, compared to the control group, accompanied by a 43% reduction in the root-to-shoot ratio. Under low-polluted condition, MNBs enhanced the plant content of Pb, Cr, Zn, and Cu by 1.9-, 1.9-, 1.2- and 1.2-fold, respectively, reducing the soil residual rates of Cr, Zn, and Cu to below 30%. Furthermore, principal component and correlation analyses revealed that soil heavy metal retention was positively correlated with total dissolved solids (TDSs), and these parameters inversely affected ryegrass growth. Membership evaluation showed the MNBs-treated group scored 0.83, much higher than the control group's 0.17 under metal stress. Ultimately, the synergistic MNBs-ryegrass system emerges as a highly efficient and promising strategy for the practical remediation of industrial soils.
Li-Xin Sun, Min Feng, Yi-Jun Ran et al.· International journal of phy...· 0 citations
Remediating calcareous soils co-contaminated with copper and arsenic remains a major challenge due to low metal bioavailability and the risk of chelator-induced phytotoxicity, which can severely limit phytoremediation success. This study investigated a synergistic strategy combining heavy metal-resistant plant growth-promoting rhizobacteria (PGPR) with precisely timed ethylenediaminetetraacetic acid (EDTA) application to improve phytoextraction efficiency in corn (Zea mays). Eight PGPR isolates were obtained from contaminated soil, and three strains (Stenotrophomonas sp. A22, Pseudomonas sp. A2 and A5) were selected based on their high resistance to Cu (up to 400 mg L-1) and As (up to 250 mg L-1), as well as multiple plant growth-promoting traits. In a controlled pot experiment, we evaluated bacterial inoculation and EDTA application at 20, 35, or 45 days after planting on plant growth, physiological performance, and metal uptake. Early EDTA addition (day 20) caused severe phytotoxicity, markedly reducing root and shoot biomass and depressing photosynthetic efficiency (Fv/Fm). In contrast, delaying EDTA application to days 35 or 45 substantially alleviated these adverse effects. PGPR inoculation, particularly with strain A5, further mitigated EDTA-induced stress and improved biomass production and physiological status. The combined PGPR-EDTA treatments significantly increased soil metal bioavailability and enhanced plant uptake, with maximum shoot Cu (214 mg kg-1) and As (99 mg kg-1) concentrations observed with strains A5 or A2 and EDTA application at day 20. Sequential extraction confirmed that these PGPR-EDTA treatments shifted metals from residual and oxide-bound pools into more soluble and exchangeable/carbonate-bound fractions. The findings support a mechanistically informed, optimized phytoremediation strategy for calcareous soils, based on the optimal timing of EDTA application and inoculation with metal-resistant PGPR.
Mohsen Hamidpour, Azar Nasirzadeh, P. Abbaszadeh-Dahaji et al.· International journal of phy...· 0 citations
Petroleum-impacted soils containing total petroleum hydrocarbons (TPH) and polycyclic aromatic hydrocarbons (PAHs) restrict land reuse and pose long-term threats to soil productivity and food security in oil-producing regions. This study evaluates the performance of mutually adapted bacterial–fungal consortia comprising Pseudomonas aeruginosa, Azotobacter vinelandii, and Aspergillus niger, with targeted NPK nutrient amendments, for accelerating hydrocarbon removal and restoring soil function for post-remediation agricultural use.
Simulated crude-oil-polluted soils (SCOPs) were treated under controlled soil glass columns (2.5 cm × 3.2 cm) at 30 ± 2 °C over 21- and 42-day periods. Microbial inocula were standardised at 1.5 × 108 cells cm−3. Nine treatment configurations evaluated live/inactive consortium members under bioaugmentation (BA) and combined bioaugmentation–biostimulation (BA+BS) conditions. TPH and PAH concentrations were quantified by GC-FID following n-hexane/dichloromethane extraction, and soil protein content served as a proxy for microbial biomass and soil quality recovery. First-order kinetic modelling and regression analysis were applied to all treatment groups. First-order kinetic modelling and Duncan's Multiple Range Test (DMRT) revealed that the ternary consortium featuring Live P. aeruginosa + Dead A. vinelandii + Live A. niger (Group A9/B9) achieved the highest overall bioremediation performance. This arrangement drove an 83.0% reduction in TPH (from 794.9 mg/kg to 138.5 mg/kg; k = 0.0416 d−1, t1/2 = 16.6 days) and a 76.4% reduction in PAHs (75.7 mg/kg to 17.9 mg/kg; k = 0.0343 d−1, t1/2 = 20.2 days), statistically outperforming biostimulated binary controls (P < 0.05). Soil protein concentration correlated positively with cumulative hydrocarbon removal (R2 = 0.71–0.89 across, p < 0.005 for BA+BS groups), confirming protein as a reliable activity indicator.
The study proposes an operational bioremediation framework incorporating consortium selection, staged nutrient dosing, pH control, moisture and aeration management, and dual GC-FID/protein monitoring. Findings demonstrate that optimised microbial co-metabolism can shorten remediation timelines, lower environmental footprint and cost relative to physicochemical treatments, and measurably restore soil functions supporting post-remediation agricultural reuse and food security in oil-impacted regions.
C. P. Chinedu, Cynthia Chinonso Etoruom, Nnaemeka Emmanuel Uhuo et al.· SPE Nigeria Annual Internati...· 0 citations
Cadmium (Cd) contamination of acidic soils poses a significant threat to ecosystem stability and crop health. This study evaluated the potential of biochar derived from the halophyte
Salicornia europaea
(SBC), a salt‐tolerant plant that grows on saline‐alkali marginal land, to remediate Cd‐contaminated acidic soil. A pot experiment was conducted using acidic soil spiked with 3 mg kg
−1
Cd and amended with SBC at 0%, 1%, and 2% (
w/w
). The results showed that compared to the control, 1% and 2% SBC treatments increased the rhizosphere soil pH by 0.7 and 1.4 units, respectively, and significantly enhanced organic matter content and cation exchange capacity. In addition, these treatments reduced the concentration of available Cd in rhizosphere soil by 14.0% and 33.9%, respectively. Furthermore, biochar promoted plant growth and increased the photosynthetic rate, while Cd accumulation in plants was significantly reduced by 51.3% and 52.6%. Metabolomic analysis revealed that SBC upregulated the tryptophan metabolic pathway, with indoleacetic acid and 5‐hydroxyindoleacetic acid being the predominant metabolites. Their accumulation in rhizosphere soil was associated with enhanced plant stress tolerance and growth. Although the soil electrical conductivity increased with SBC addition, no negative effects on plant growth were observed. These findings indicate that SBC can effectively immobilize Cd, improve soil quality, and facilitate plant growth in acidic contaminated soils, thus offering a promising strategy for sustainable remediation. This approach suggests a potential pathway for utilizing resources from marginal lands to remediate acidic contaminated soils, thereby contributing to sustainable land management and environmental protection.
Shao-Qing Ge, Zhenyong Zhao, Ke Zhang et al.· Land Degradation & Devel...· 0 citations
Citric acid (CA) and nitrogen (N) fertilizers have been widely applied to enhance phytoremediation of various contaminated soils, yet their combined effects and underlying mechanisms in cadmium (Cd)–polycyclic aromatic hydrocarbon (PAH) co-contaminated systems remain poorly understood. Here, we investigated the combined effects of CA and ammonium nitrate on the phytoremediation of Cd–phenanthrene (Phe) co-contaminated soil using marigold (Tagetes patula L.), with random forest, mantel tests, and structural equation modeling employed to explore hypothesized pathways and associations. The results demonstrated that combined CA and N application significantly promoted plant growth, Cd uptake, and Phe dissipation. Among the tested treatments, the low-dose combination (1 g CA + 0.1 g N pot−1) increased plant biomass by 88%, enhanced shoot Cd uptake by 121%, and achieved a Phe dissipation rate of 76.56%, representing the optimal remediation strategy. Mechanistically, the synergy between CA and N extends beyond simple growth promotion—N drives biomass production and, independently, facilitates Cd mobilization through rhizosphere acidification, while CA enhances contaminant bioavailability and buffers N-induced salt stress, together maintaining rhizosphere ionic homeostasis for efficient Cd translocation and Phe dissipation. This study provides a mechanistic framework for designing combined amendment strategies to enhance phytoremediation of co-contaminated soils.
This study explores phytomycoremediation, a dual-biological approach combining fungal organic acid production and plant-based phytoextraction to increase uranium mobility and uptake from contaminated soils. A pot experiment was conducted using uranium-contaminated soil originating from a former uranium mining area in Zadní Chodov, Czech Republic. The soil was amended with spent mushroom substrate of the white rot fungus Pleurotus ostreatus, alongside the cultivation of Raphanus sativus (Brassicaceae). Two soils differing in uranium concentrations were used. The cultivation period lasted 2 months, during which soil solution was collected in weeks 2 and 6 using soil moisture samplers and analysed for low-molecular-weight organic acids (LMWOAs). In addition, uranium and other potentially toxic elements (including cadmium, lead, and arsenic) were quantified in the plant biomass. Among the detected LMWOAs, citrate concentrations increased significantly (p < 0.05) in the soil solution from the fungus-amended soil samples. However, the uranium concentrations in the plant tissues remained relatively low, with uranium predominantly retained in roots. Moreover, uranium uptake by plants tended to decrease in the presence of the fungus, which was confirmed as significant (p < 0.05) in roots. This pattern suggests that P. ostreatus SMS did not enhance uranium phytoextraction under the tested conditions and may have reduced plant-accessible uranium, although direct measurements of uranium speciation and fungal uranium retention are required to confirm this mechanism. Although P. ostreatus SMS increased LMWOA concentrations, particularly citrate, this did not translate into enhanced uranium uptake by plants. Further research involving additional fungal and plant species, as well as optimisation of environmental conditions, is needed to improve phytomycoremediation strategies for uranium-contaminated environments.
Karlygash Zhussupova, J. Száková, Martin Čermák et al.· Sustainability· 0 citations
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